NO-JIRA: ctest runs all tests in the build tree, added valgrind support.

Updated README with info on running tests.

Wrapper script tests/run.py to run tests, allows ctest to run with no environment settings.
(tests/run.py replaces build_env.py)

System tests also run by ctest in the build tree.

Valgrind support added, OFF by default: many memory errors, slows down system tests.
To try it out: cmake -DUSE_VALGRIND=ON

Note: test.sh behaves as before, it runs unit tests in the build and system tests in the install tree.

git-svn-id: https://svn.apache.org/repos/asf/qpid/dispatch/trunk@1603289 13f79535-47bb-0310-9956-ffa450edef68